Python access to devices present in a service

[franjorge]

Hello,

I have the following yang model:

module cr-art {
  namespace "http://example.com/cr-art";
  prefix cr-art;
...
  list cr-art {
    key DEVICE;
    uses ncs:service-data; ncs:servicepoint cr-art-servicepoint;

    leaf DEVICE {
      type leafref {
        path "/ncs:devices/ncs:device/ncs:name";
      }
    }
...

Now I am trying to get a list of all the devices configured in service cr-art under python. So far I have tried:

        for i in root.cr_art.cr_art.DEVICE:
            self.log.info(i)

this returns:

Error: Python cb_create error. 'List' object has no attribute 'cr_art'

I have also tried:

        for i in root.cr_art.DEVICE:
           self.log.info(i)

Which returns:

Error: Python cb_create error. 'List' object has no attribute 'DEVICE'

The only thing that does not return an error is:

        devices_in_cr_art = []
        for i in root.cr_art:
          devices_in_cr_art.append(i)
        self.log.info(devices_in_cr_art)

But it prints the following in the logs:

 - [ListElement name=cr-art tag=1779143679 keys={artmad1-01}, ListElement name=cr-art tag=1779143679 keys={artmno1-01}]

What I need is only the values of "keys", but I do not seem to be able to access them in an easy way.

Any suggestion, please?

Thanks

[tcragg1]

You should be able to access them by calling the DEVICE object within each ListElement as you iterate over the List. Try the following:

        devices_in_cr_art = []
        for i in root.cr_art:
          devices_in_cr_art.append(i.DEVICE)
        self.log.info(devices_in_cr_art)

[franjorge]

Thanks,

That worked!

In fact, what I was trying to do is to check if a value is in the list of devices configured for the service. Something like:

        for rv in service.ROUTER_VECINO:
          if rv.NOMBRE in root.cr_art.DEVICE:
            self.log.info("Yes, it is")

But that rises an error. What works, thanks to your previous suggestion, is:

        devices_in_cr_art = []
        for i in root.cr_art:
          devices_in_cr_art.append(i.DEVICE)

        for rv in service.ROUTER_VECINO:
            if rv.NOMBRE in devices_in_cr_art:
            self.log.info("Yes, it is")

I am now wondering if there is a better way to do this or this is the only valid approach.

[tcragg1]

The NSO List object type in python has a method called "exists" that you may be able to use for this. I think in your case it would look something like the following:

for rv in service.ROUTER_VECINO:
    if root.cr_art.exists(rv.NOMBRE):
    self.log.info("Yes, it is")

This should iterate over service.ROUTER_VECINO, and for each value test whether it exists as a key in the list root.cr_art.

[franjorge]

Great! It works.

Where can I learn about other methods available for List objects in NSO? Is there any document or man page where I can find them?

Thanks,

Fran

[tcragg1 · Accepted solution]

Yes, there is documentation for the python APIs inside the documentation folder of NSO. If you go to the root folder for the documentation, you should then find the python API docs at the following path: doc/api/python/index.html

For the methods of the basic YANG object types (List, Leaf, Container, etc.), check out the ncs.maagic link from that index webpage.

[vleijon · Accepted solution]

As an alternative, you can run pydoc ncs.maagic.List at the commandline.

[franjorge]

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@vleijon wrote:
As an alternative, you can run pydoc ncs.maagic.List at the commandline.

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Thanks, this is very helpful!

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